This invention relates to improvements in a pendulum drawing machine. More specifically, it relates to improvements in the joint and mounting means for such machines.
Pendulum drawing machines are known in the art. See, for example, U.S. Pat. Nos. 1,869,951; 3,143,807; 3,324,556; 3,494,037; and 3,977,085. A pendulum drawing machine is used for making various designs on a sheet of paper positioned on a base such as a table surface. Basically, the machine comprises two vertically positioned pendulum arms having weighted ends, a mounting means for pivotally mounting the pendulum arms to a table or other base, a pivot means for pivotally supporting the pendulum arms on the mounting means, two horizontal arms pivotally attached at each of their ends to the vertical pendulum arms and attached at their opposite ends to a penholder, which holds a pen for drawing designs on the sheet. One of the horizontal arms usually is pivotally attached to the penholder.
The pendulum drawing machine creates drawings of a geometrical nature by combining the motion of the two independent driving forces--the pendulum arms. Each pendulum arm oscillates at a rate determined by its length and the position of the weight affixed to its bottom end. As each pendulum swings, the top of the arm (which is above the pivot axis) moves back and forth. The pendulums are pivotally mounted so that they swing at right angles to each other, and are positioned such that the two horizontal arms meet at right angles at the penholder. The arm joints and pivots allow the penholder to describe a path which is the sum of the two motions of the horizontal arms. As the drawing progresses, the pendulum arms will swing back and forth, causing figures to be drawn as circles, ovals, straight lines or an infinite combination of these. The friction of the pen and assorted joints and pivots causes the motion of each pendulum to terminate slowly. The drawing thus produced slowly converges to a stationary point.
The above-cited patents describe machines which vary in the manner in which they are mounted to a horizontal surface or table, in the configuration of the pendulum arms, in the pivot means for pivotally attaching the pendulum arms to the horizontal surface, in the joint means for pivotally attaching the horizontal arms to the pendulum arms or to the penholder, or in other ways such as, for example, in U.S. Pat. No. 3,143,807, wherein a flexible wire is used for connecting each of the pendulum arms with the penholder, rather than rigid, horizontal arms. The machine of the present invention differs from all these prior patents in the joint means for attaching the horizontal arms to the pendulum arms and to the penholder and in the mounting means for mounting the pendulum arms to a table or horizontal surface.
The joint means of the prior patents are either crude (U.S. Pat. No. 1,869,951) or comparatively complex (U.S. Pat. Nos. 3,324,556 and 3,977,085). Moreover, several of the previously disclosed joint means have either less than or more than the desired degrees of freedom of the joint means of the present invention, as is described below. Moreover, the joint means of the present invention generally dissipate less energy through friction than do the means of the prior patents. This allows the machine to operate for a longer period of time on a given energy input and thereby to produce more elaborate drawings.
The mounting means of the present invention comprises a board which can be placed diagonally across a corner of the horizontal surface or table. The board contains the pivot means which pivotally supports the pendulum arms on the mounting means. Thus, the drawing machine of the present invention can easily be positioned for use on almost any table without advance preparation. Additionally, this mounting means is simple in design and thus very economical.
In summary, the simple, but very efficient and effective, joint and mounting means of the present invention provide a pendulum drawing machine that is considerably less complex in design and less bulky in structure than those previously disclosed. Consequently, it is more economical and more easily packagable for sale. The simplicity of the present invention greatly enhances its economic appeal.
The advantages and objects of the invention will become further evident from the detailed description of the invention given below.